However,there was no loss of antioxidant activity by the natural extract. The
EC50 value of each sample of natural extract obtained at different
times during the assay indicated that the antioxidant activity of the natural
extract remained constant (see Table 1). No significant differences
in statistical terms (p b 0.05%) were found between each sample of natural
extract. The weight reduction after exposure to a temperature of
200 °C for 120 min was 23.1% (w/w) showing significant differences
with respect to extract sample before temperature exposure; the total
phenolic contentwas around 60% in all samples (see Fig. 1B) and the antioxidant
activity increased slightly (see Table 1). No significant differences
in statistical terms were found within different natural extract
samples collected at different times of exposure to temperature,
which means that the antioxidant activity remain constant over the
heating time except for the follow conditions: 120 min at 200 °C.
These results can be attributed to the presence of compounds with
lowor even no antioxidant activity in the volatile fraction of the extract,
so that there is a relative increase in the concentration of the active compounds
resulting in more active extracts. The results obtained in the
present study are consistent with previous findings. Cruz, Conde,
Domínguez, and Parajó (2007) showed that temperature has only a
slight influence on the phenolic content and antioxidant activity of natural
extracts obtained from industrial wastes, which showed a greater
ability than synthetic antioxidants (BHT and BHA) to retain antioxidant
activity after heating at 100, 150 and 200 °C for 2 h. These authors also
suggested that the compounds resulting from the thermal degradation
may be more active than those in the initial extracts (Cruz et al.,
2007). Taking into account that LDPE and EVA extrusion is carried out
at 150 °C for 6min, the natural extract can be blendedwith the polymer
(at 160 °C)with only a slight loss of active compounds and no loss of the
antioxidant capacity.